There exists an image integration technology for generating an image having high visibility by selecting multiple types of images differing in image features, such as a visible image and an infrared image, an RGB image and a narrowband image, or the like, depending on the scene (condition of the image capture object, condition around the image capture object, or the like) and integrating (combining) the selected images. For example, near-infrared images achieve high visibility when a haze has occurred or in a high dynamic range environment, while narrowband images obtained by image capture from a satellite or a drone are suitable for use for monitoring the seas and vegetation regions. Further, widely available on the market are monitoring devices including an irradiation device for irradiating the object with invisible light, such as a near-infrared light source, and a camera for acquiring an image with a high signal level and a low noise level and being suitable for monitoring scenes in the nighttime. By combining one of such images differing in the image features with a visible image, an object or target that should be paid attention to can be distinguished with ease even when a scene in which the distinction is difficult only with a visible image has been captured.
Patent Reference 1 describes an image processing method for accurately enhancing edges included in a first image for display, among the first image and a second image obtained by image capture of the same object in different conditions, by using edge components of the second image.